Stylus assembly



M. S. COHEN STYLUS ASSEMBLY Feb, 13, 1968 Filed Sept. 14, 1964 UnitedStates Patent Ofiiice 3,369,254 Patented Feb. 13, 1968 3,369,254 STYLUSASSEMBLY Milton S. Cohen, Arlington, Mass., assignor, by mesneassignments, to Arthur D. Little, Inc., Cambridge, Mass., a corporationof Massachusetts Filed Sept. 14, 1964, Ser. No. 396,337 4 Claims. (Cl.346-139) ABSTRACT OF THE DISCLOSURE A stylus assembly for writing onelectrosensitive paper comprising a wire stylus mounted within aninsulation sleeve and inclined in a direction opposite the direction ofmovement of the paper relative to the stylus, and a weighted member ortension spring detachably secured to the stylus for biasing it againstthe paper.

This invention relates to dry electrosensitive writing systems and, moreparticularly, to a new and improved writing stylus assembly for use insuch systems.

Dry electrosensitive writing systems, as such, are well known in theart, Such systems generally comprise means for applying electricalenergy to an electrosensitive paper to cause the portion of the paper towhich the electrical energy is applied to be broken down resulting in achange of color. The electrical energy is usually applied between ametal stylus moving lightly over the coated surface of theelectrosensitive paper and a metal platen or drum with which the back ofthe paper makes good contact. For satisfactory writing, the drum orstylus must be resiliently mounted to provide a substantially uniformstylus-topaper pressure. The optimum pressure required depends somewhaton the relative speed of the stylus and paper. In some systems thestylus is moved relative to the electrosensitive paper; in others thereverse may be true.

The material most generally used in styli is fine drawn tungsten wireapproximately 0.010" in diameter. Since an accurate stylus-to-paperpressure can easily be obtained by utilizing relatively fixed stylusmounting, the advantages of using a stylus which has a low rate of wearand erosion are obvious. Tungsten, however, has several characteristicswhich reduce its desirability. The most serious of these is that drawntungsten wire has a fibrous crystal structure. As the stylus wears, theend of the wire becomes splintery or broom-like. The worn stylus tendsto pick up portions of the insulating coating of the recording paper andbecomes loaded with the insulation and/ or develops sharp edges whichscratch or gorge the electrosensitive surface of the paper. In eithercase, the quality of the writing and copy are markedly decreased.

A hard drawn steel wire, e.g., piano or music wire,

wears smoothly and avoids the undesirable effects caused by tungstensplintering. Steel wire has not been widely used in the past because itwears much more rapidly than does tungsten and the stylus mustfrequently be adjusted and/ or replaced.

An object of the present invention is to provide a stylus mountingassembly which adjusts itself to compensate for wear.

Another object is to provide a stylus assembly of the type mentionedwhich insures a continuously substantially uniform stylus-to-paperpressure irrespective of the wearing or erosion of the stylus.

Still another object is to provide an assembly of the type mentioned inwhich a worn stylus may easily be removed and replaced.

The invention accomplishes the above mentioned objects by providing acylindrical insulating sleeve mounted in a fixed relationship to theelectrosensitive paper. The

stylus extends through the sleeve into engagement with theelectrosensitive paper, and means are provided for mechanically biasingthe stylus towards the paper with a predetermined, continuous pressure.

For a fuller understanding of the natures and objects of the invention,reference is now made to the following detailed disclosure of preferredembodiments thereof taken in conjunction with the accompanying drawingswherein:

FIG. 1 is a sectional view of apparatus comprising one form of thepresent invention; and

FIG. 2 is a sectional view of an alternative embodiment of theinvention.

Reference is now made to drawings which illustrate stylus systems forwriting on electrosensitive paper. The paper is shown mounted on arotating drum for movement relative tothe stylus. As illustrated, eachof the systems comprises a steel stylus 10 mounted on a rigid supportarm 12 and adapted for Writing on a piece of electrosensitive paper 14wrapped around a cylindrical drum 15. Electrical energy is applied tothe stylus by a connecting wire 16. The stylus is held in a positionslightly inclined to the surface of the drum by an insulating cylinderor sleeve 18 surrounding the stylus and extending through support arm12. The axis of the insulating sleeve is slightly inclined from theperpendicular relative to the surface of drum 15. The inside diameter ofsleeve 18 is slightly greater than the diameter of stylus 10 so thatthere is a slip fit between the stylus and sleeve. The angle at whichthe point of the stylus engages the surface of the electrosensitivepaper wrapped around the drum is not critical. It is only desirable thatthe stylus be slightly inclined relative to the surface of the drum sothat it will be dragged across the electrosensitive paper as the paperis moved relative to the stylus. If the stylus were perpendicular orinclined in the opposite direction, it would have a tendency to dig intothe surface of the electrosensitive paper.

In the embodiment illustrated in FIG. 1, stylus 10 is biased towardsdrum 15 by a helically wound spring mounted coaxially with andsurrounding the upper portion of sleeve 18 (the portion of the sleeve onthe side of support arm 12 most distant from the drum). A cylindricalinsulating ring 20 surrounds sleeve 18 at a point closely adjacentsupport arm 12 and intermediate spring 22 and the support arm so thatthe spring and support arm are electrically insulated from each other.Spring 22 extends from adjacent insulating ring 20 axially along thestylus to a point above the upper end of sleeve 18. As illustrated,spring 22 is loosely fitted around sleeve 18 and a retaining collar 24is provided to secure the lower portion of the spring to the sleeve. Atightly wound helical extension spring 26 is attached to the upper endof spring 22 in position for engaging the adjacent portion of stylus 10and securing it relative to the upper end of spring 22. Connecting wire16 is secured to spring 22 and electrical energy conducted from the wireto the stylus through springs 22 and 26.

As illustrated, spring 22 is axially extended from its relaxed positionso that stylus 10 is forced against the electrosensitive paper. Spring22 is preferably constructed to produce a relatively constant axialforce so that, as stylus 10 wears away, the stylus-to-paper pressurewill remain substantially constant for a relatively long period of time.When the stylus has worn so much that it must be replaced, it can easilybe removed from the mounting by slightly extending or bending spring 26and manually drawing the stylus upward through sleeve 18. A new stylusmay then be dropped into place and spring 26 released to engage it.

Reference is now made to FIG. 2 which illustrates an alternativeembodiment of the invention. This embodimen: enters from thatillustrated in FIG. 1 in that the stylus is biased towards the drum by aweight 26 secured to an upper portion of the stylus by thumbscrew 28rather than by a spring. Connecting wire 16 is secured directly to theweight. The stylus-to-paper pressure is a direct function of the size ofthe weight and will remain constant until so much of the stylus wearsaway that the weight rests upon the top of sleeve 18. At that time theworn stylus may easily be replaced by merely loosening thumbscrew 28.This alternative embodiment, unlike that illustrated in FIG. 1, islimited to use in systems in which the stylus is above theelectrosensitive paper and the speed of the stylus relative to the paperis low enough so that inertial characteristics of the weight are notobjectionable.

It should be obvious that the invention herein described is notrestricted to the use of steel styli but is adapted for use with anyconducting stylus material. Since certain other changes may be made inthe above apparatus without departing from the scope of the inventionherein involved, it is intended that all matter contained in the abovedescription or shown in the accompanying drawings shall be interpretedas illustrative and not in a limiting sense,

What is claimed is:

1. A writing stylus assembly for writing on electrosensitive papermounted for movement relative to the stylus assembly comprising, incombination:

a support arm mounted adjacent and extending above the electrosensitivepaper;

a cylindrical insulating sleeve secured to the portion of the supportarm above the paper with the axis of the sleeve slightly inclined from adirection perpendicular to the paper in a direction opposite thedirection of movement of the paper relative to the stylus assembly;

a cylindrical wire stylus having a diameter slightly less than thediameter of the sleeve extending axially through the sleeve;

a weighted member having a weight substantially equal to the desiredpressure between the stylus and electrosensitive paper detachablysecured to the stylus at a point above the upper axial end of the sleevefor biasing the stylus towards the paper with a predetermined force; and

an electrically conductive wire secured to the weighted member forapplying electrical energy to the stylus.

2. A writing stylus assembly for writing on electrosensitive papermounted for movement relative to the stylus assembly comprising, incombination:

a support arm mounted adjacent the electrosensitive a cylindricalinsulating sleeve secured to the support arm with the axis of the sleeveslightly inclined from a direction perpendicular to the paper in adirection opposite the direction of movement of the paper relative tothe stylus assembly;

a cylindrical wire stylus having a diameter slightly less than theinside diameter of the sleeve extending axially through the sleeve;

a helical stylus biasing spring mounted coaxially with the insulatingsleeve on the side of the support arm most distant from the paper andelectrically insulated from the support arm with the portion of thespring nearest the paper secured to the insulating sleeve;

stylus engagement means securedto an upper portion of the spring anddetachably secured to the stylus tor applying the force of the stylusbiasing spring in tension to the stylus to force the stylus against thepaper with a predetermined force; and

an electrically conductive wire electrically connected to the stylus forapplying electrical energy thereto, the stylus and insulating springbeing electrically insulated from the support arm.

3. The stylus assembly of claim 2 wherein the stylus engagement meansincludes a tightly Wound helical spring secured to an upper portion ofthe stylus biasing spring substantially perpendicular to the axisthereof with the coils of the tightly wound spring detachably secured tothe stylus.

4. The stylus assembly of claim 3 including an insulating collarsurrounding and secured to the sleeve at a point closely adjacent thesurface of the support arm and wherein the sleeve extends through thesupport arm and a portion of the stylus biasing spring is secured to thesleeve at a point closely adjacent the collar.

References Cited UNITED STATES PATENTS 456,668 7/1891 Boyer 3461392,380,467 7/1945 Ressler 346-139 2,404,975 7/1946 Mathes 346-4392,442,561 6/1948 Finch 346139 2,850,350 9/1958 Wise 34674 FOREIGNPATENTS.

730,260 1/1943 Germany.

730,844 6/1955 Great Britain.

212,460 2/1941 Switzerland.

RICHARD B. WILKINSON, Primary Examiner.

JOHN W. CALDWELL, Examiner.

J. A. ORSINO, I W. HARTARY, Assistant Examiners,

